Which has the most impact on your energy bill: the green things you do (like driving a hybrid and re-insulating your house), the type of house you live in or where you live?

It turns out, a family living near transit in a compact neighborhood saves more energy than an energy-efficient family living in the suburbs.

"Housing that is located in a walkable neighborhood near public transit, employment centers, schools, and other amenities allows residents to drive less and thereby reduces transportation costs,” says Daniel Hernandez of the Jonathan Rose Companies, a green real estate firm that just completed a study to figure out what impacts household energy use most.

Cutting the Most from Your Energy Bill

Done in partnership with the U.S. Environmental Protection Agency, the study uses British Thermal Units (BTU)—a measure of total energy use—to calculate how housing type, household location and transit access influence a family’s energy use relative to efficient building and vehicle technology.

A family living in a typical “detached” house in the suburbs can cut their energy bill by 33 percent by greening their buildings and cars, which reduces their energy use by an average of 82 million BTU per year. But if the family moves to a similar house with better access to transit, but no green features or efficient cars, they can cut their energy use by an average of 39 percent (93 million BTU per year). If the family also improves their home energy efficiency by 20 percent and gets a hybrid car their total energy savings jump to 54 percent.

Credit:Jonathan Rose Companies

The researchers got similar results for “single family attached” houses, referring to townhouses, and “multi-family” homes, meaning apartments or condos with multiple families living in the same building. A family that moves from a typical suburban house to an apartment close to transit saves an average of 61 percent off their energy bill (or 147 million BTU each year). If they also improve their personal energy efficiency they can cut their energy use by 72 percent, saving up to 173 million BTU annually.

Find Out What Your Community Should Have

When you’re next in the market for a new house make sure you can easily take a bus, train or bike to work instead of relying on your car. Also, look for a neighborhood that incorporates smart development (aka smart growth).

Smart growth involves “‘location efficient’ development, which has a more compact design, higher-density construction, and includes a diverse mix of uses,” says Hernandez. This means mixing retail and commercial buildings in with residential areas so that residents can walk instead of drive to pick up groceries; providing widespread access to energy-efficient public transportation (for example, ensuring streets integrate pedestrian, bike and bus lanes); and constructing houses that share walls to reduce heat loss.

If you won’t be moving homes any time soon, work to improve the neighborhood you live in to make it more energy-efficient and transit-friendly. Become an active member of your community by telling local, state and federal policy-makers about the importance of smart housing and transportation to make your neighborhood more energy-efficient, affordable and livable.

While the Jonathan Rose Companies study is based on national averages and doesn’t look at specific regions, there are many cities taking on smart growth development strategies to provide residents with more affordable housing and transportation options. Take Lincoln, Nebraska, for example. This 2011 Smarter City for Transportation has been enforcing strict zoning laws since the early 1990s to promote compact development and avoid suburban sprawl. This smart development strategy shortens residents’ daily commutes to less than 17 minutes each way, well below the national average, and helps provide widespread bus access to all neighborhoods.

Similarly, since the 1970s city planners in Portland, Oregon (another 2011 Smarter City for Transportation) have embraced transit-oriented, dense development by establishing an urban growth boundary. Today, 86 percent of commuters in Portland save money and energy by choosing public transit over driving.

Energy-efficient, smart growth is important both for saving money as well as reducing carbon emissions, among other environmental impacts. “Buildings and transportation together account for about 70 percent of energy use in the United States and are responsible for about 62 percent of U.S. greenhouse gas emissions,” according to the U.S. EPA. “Creating more energy-efficient communities and buildings would reduce our impact on climate change and save people money on household energy costs.”

The most effective way to reduce your energy use and emissions is to live in both a green house and a green community. The most energy efficient and affordable lifestyle involves living in an apartment or condo, using public transit, andgreening your residence. But remember, even if you have a house in the suburbs you can cut your energy by a third by improving the energy efficiency if your home and travel.

“People can do many things to reduce their energy use: install energy-efficient light bulbs, carpool or walk or buy Energy Star appliances, among other things,” the EPA said in announcing the study results. “But the way in which we plan and build our communities also has a significant role to play in creating a more environmentally and economically sustainable future.”